Machines such as dozers, loaders, excavators, motor graders, and other types of heavy equipment use one or more hydraulic actuators to move a work tool. These actuators are fluidly connected to a pump on the machine that provides pressurized fluid to chambers within the actuators. As the pressurized fluid moves into or through the chambers, the pressure of the fluid acts on hydraulic surfaces of the chambers to affect movement of the actuator and the connected work tool. When the pressurized fluid is drained from the chambers, it is returned to a low pressure sump on the machine.
One problem associated with this type of hydraulic arrangement involves efficiency. In particular, the fluid draining from the actuator chambers to the sump has a pressure greater than the pressure of the fluid already within the sump. As a result, the higher pressure fluid draining into the sump still contains some energy that is wasted upon entering the low pressure sump. This wasted energy reduces the efficiency of the hydraulic system.
One method of improving the efficiency of such a hydraulic system is described in U.S. Pat. No. 7,444,809 (the '809 patent) issued to Smith et al. on Nov. 4, 2008. The '809 patent describes a hydraulic regeneration system for a work machine. The hydraulic regeneration system has a tank, a primary source, an actuator, an accumulator, and an energy recovery device. The primary source is configured to draw fluid from the tank and discharge the fluid at an elevated pressure to the actuator. During movement of the actuator, waste fluid from the actuator is directed into the accumulator for storage. This stored fluid is then directed from the accumulator through the energy recovery device to recover some of the energy from the waste fluid, thereby improving the efficiency of the hydraulic regeneration system.
Although the system of the '809 patent may have improved efficiency compared to a conventional hydraulic system, it may nonetheless be in need of improvement. Specifically, the system of the '809 patent requires complex valving to control fluid flows between the actuator, the accumulator, the energy storage device, and the primary source. This complex valving may be difficult to control and increase a cost of the system. In addition, energy from pressurized fluid used to swing a machine may not be recovered by the system of the '809 patent.
The disclosed hydraulic control system is directed to overcoming one or more of the problems set forth above and/or other problems known in the art.